1. Field of the Invention
The present invention relates to a unitary rod gland assembly and, more particularly, to a simple, lightweight, low-cost, unitary rod gland assembly.
2. Description of the Prior Art
In the fields of pneumatic and hydraulic cylinders, accumulators, actuators, regulators, valves, and the like, a common mechanical component is a rod gland assembly which is adapted to be positioned in a cylinder, between the cylinder bore and a piston rod. The rod gland assembly is a stationary member positioned at one end of the cylinder and includes a rod gland which is responsible for supporting multiple seal elements for performing multiple functions. Conventional rod glands are made either from aluminum, brass, steel, or cast iron.
Initially, since it is necessary to prevent metal-to-metal contact between the same materials, the rod glands and the piston rods are either made from dissimilar materials or bearings are positioned in grooves in the rod gland's inner surface, which bearings physically contact the piston rods to provide a bearing surface.
Since it is necessary to provide a seal between the outer surface of the rod gland and the cylinder bore, a groove is generally positioned in the rod gland's outer surface for receipt of O-rings or gaskets to pevent leakage of the fluid within the cylinder between the rod gland outer surface and the cylinder bore. Since it is also necessary to provide a dynamic seal between the inside surface of the rod gland and the piston rod, it is conventional to provide a groove in the inner surface of the rod gland, adjacent the internal side thereof, for receipt of a rod seal which prevents leakage of the fluid within the cylinder along the pistion rod.
It is also necessary to prevent contaminates from entering into the cylinder as the piston rod reciprocates through the rod gland. Therefore, it is common to provide an additional groove in the inside surface of the rod gland, adjacent the external side thereof, for receipt of a wiper/scraper which prevents the passage of contaminates along the piston rod into the cylinder as the piston rod moves into the cylinder.
It can therefore be seen that a conventional rod gland assembly consists of a large number of interconnected parts. A rod gland assembly requires multiple O-rings, gaskets, and/or seals made from rubber, plastic, leather, and the like. The separate rod gland and seal element assemblies are expensive due to the need to manufacture each part individually.
An additional major expense which results from manufacturing a rod gland this way stems from the requirement of holding very close tolerances in cutting the grooves in the gland's inner and outer surfaces so that the seals inserted therein perform properly. Furthermore, each seal element has two potential leakage paths. For example, the bore seal has leakage paths between the bore and the bore seal and between the bore seal and the rod gland.
Since there are multiple components in a conventional rod gland assembly, assembly time is also longer and this adds to the expense. Where the rod gland is manufactured from steel, aluminum, or brass, it is quite heavy. There is also the possibility of one of the seal elements becoming dislodged during assembly of the rod gland assembly into the cylinder. In spite of the above disadvantages, rod gland assemblies have conventionally been made in the manner described above.